PROJECTABSTRACT Therearetwobigchallengestoreducingthenumberofsubstanceusedisorders(SUDs)intheUnitedStates: 1)Almost90%ofthe21.7millionpeoplewhosufferfromSUDsareneverprofessionallydiagnosedandnever seektreatment[1]and2)treatmentforthesmallminoritythatdoesseekhelpisnotveryeffectivewithrelapse ratesestimatedtobebetween65%and90%withinthefirstyearaftertreatment,dependingonthesubstance thatisbeingmisused[2]. TheClinicalAddictionRecoveryInstitute (C.A.R.I.),aMentorontheGoLLCcompany,aimstoaddressbothof those challenges by developing a continuous monitoring system based on an injectable, subcutaneously implanted biosensor, approximately the size of a grain of rice that can detect and monitor substance use byproducts in the interstitial fluid. The C.A.R.I system for detecting and monitoring substance misuse will integrate wearable sensor technology with an already developed mobile smartphone application that will enablephysicianstomoreeasilydetect,monitorandtreatsubstancemisuse. Currentlynoothersolutionsexist thatcandetectmultiplesubstancesandmeasurethemcontinuouslyovertime.ThisPhaseIprojectwillfocus on the detection of an opioid substance and will test the hypothesis that a minimally invasive injectable biosensorwithaminimumlifetimeofonemonthcansuccessfullymeasureabiomarkerneededtodetectopioid use.Aim1ofthisprojectwilldevelopalow-powerelectrochemicalinjectablebiosensorthatcancommunicate wirelesslywithawearabledeviceandsmartphonewhileAim2willinvolvetheselectionanddevelopmentofan electrochemicalopioidassayforuseinthebiosensor.Theresultsfromthesestudieswillprovidenotonlythe proof of concept that opioid use can be detected in interstitial fluid, but also the basis for the implantable biosensorcomponentoftheproposedC.A.R.I.system,whichwillbeavastimprovementovertheintermittent monitoring data that is currently available via self-reporting, urine screening, and blood testing. When fully developed, the proposed C.A.R.I. system will enable clinicians to be more precise with dosing and safety planning for opioid use treatment, thereby lowering relapse rates and improving treatment outcomes for patients.